Dynamic heat flow meter for measuring thermal properties of insulation or the like, and corresponding method

ABSTRACT

A dynamic heat flow meter is provided which introduces a measured air flow into the system adjacent the test sample (e.g., insulation product), for which thermal properties are to be measured. The heat flow meter then measures thermal properties (e.g., thermal conductivity and/or heat capacity) of the test sample taking into account air flow through and/or adjacent the test sample.

This application relates to a dynamic heat flow meter for measuring thethermal properties of a material (e.g., insulation such as fiberglassinclusive insulation, or any other suitable material). The dynamic heatflow meter takes air flow into account when measuring thermal propertiesof a material. A corresponding method is also provided.

BACKGROUND OF THE INVENTION

The instant application relates to a heat flow meter, and method, fortesting thermal properties of materials including thermal conductivityand/or heat capacity.

Thermal properties, such as thermal conductivity, are important physicalproperties of solids. Heat flows through a solid that has a temperaturegradient across its volume. The thermal conductivity of a specimen canbe measured directly by measuring the heat flux resulting from a knowtemperature gradient across a known thickness.

A one-dimensional form of the Fourier heat flow relation is sometimesused to calculate thermal conductivity under steady-state conditions:k=Q (ΔX/ΔT), where “k” is thermal conductivity, “Q” is a heat flow per aunit surface area (heat flux), and ΔT is a temperature difference overthe thickness ΔX.

Prior Art FIG. 1 illustrates a conventional static heat flow meter formeasuring the thermal conductivity of a test sample (e.g., piece ofinsulation such as fiberglass). The test sample or specimen is locatedbetween two flat plates, and the plates are maintained at known, butdifferent, temperatures. As heat flows through the test sample from thehot side to the cold side, a heat flux transducer (not shown) measuresthe amount of heat transferred. Thermocouple(s) or other temperaturemeasuring device(s) measure the temperatures of each of the two plates(i.e., of the so-called hot and cold plates). These values are thenplugged into the above-listed equation, so that the thermal conductivityof the test sample or specimen can be calculated based on the measuredvalues. Such measurements are often done in accordance with standardtesting methods such ASTM C 518, which is incorporated herein byreference. It is in such a manner that insulation products such asfiberglass batts are assigned so-called “R-values”—based on their steadystate or static measured thermal properties per ASTM C 518 (e.g., R11fiberglass insulation batt, etc.).

Unfortunately, the standard testing device of FIG. 1 discussed abovedetermines thermal properties of the test sample via steady state orstatic testing, where there is no air flow (i.e., there is zero airmovement introduced into the testing equipment during the testing).Thus, measurements from such devices can be deceiving as will beexplained below.

When insulation (e.g., fiberglass insulation batt, fiberglassloose-fill, cellulose loose-fill, combination/laminate of fiberglass andfoam insulation, or the like) is provided in a vertical wall cavity of ahome (e.g., between two-by-four studs as is known in the art), it hasbeen found that air flow (e.g., due to wind or the like in theenvironment surrounding or adjacent to the home) through the wall canhave an affect on insulation properties. Contributions to total buildingheating or cooling load include the change in enthalpy of air movingthrough an insulation (e.g., fiberglass) and the heat flux through theinsulation due to the imposed thermal gradient. The two effects are notindependent since the air movement affects the temperature distributionin the insulation. One may experience an example of air flow in anexterior wall of a home by feeling a cool draft in the winter when oneputs his or her hand adjacent an electrical outlet. Such air flows in orthrough walls can reduce the thermal performance of insulation, sinceinsulation such as fiberglass is not an air barrier as it does not stopair flow.

Heretofore, there has been no efficient way to measure the effect of airflow on insulation products. In particular, there has been no way toquantify how much air flow reduces the thermal performance of certaininsulation products. Unfortunately, the conventional heat flow metershown in FIG. 1 and discussed above does not take air flow into accountwhen measuring thermal properties of the test sample.

In view of the above, it will be apparent to those skilled in the artthat there exists a need in the art for a heat flow meter, and method,for measuring thermal properties of a product (e.g., insulation product)in a manner which takes into account dynamic air flow.

BRIEF SUMMARY OF EXAMPLES OF THE INVENTION

In certain example embodiments of this invention, a heat flow meter isprovided which introduces a measured air flow into the system adjacentthe test sample (e.g., insulation product) to be measured. The heat flowmeter then measures thermal properties (e.g., thermal conductivityand/or heat capacity) of the test sample taking into account air flowthrough the test sample.

By taking into account intentionally introduced and measured air flowthrough and/or across the test sample, one can determine how effectivethe particular sample would be in real-world conditions where wind (andthus air flow in/through home walls) is a frequent occurrence. Thispermits one to determine which types of insulation may be effective incertain types of environments.

In certain example embodiments of this invention, there is provided amethod of measuring thermal properties of insulation, the methodcomprising: in a housing, providing first and second plates; positioninga test sample of insulation between the first and second plates;providing the first and second plates at different temperatures when thetest sample is therebetween; introducing an air flow into the cavity onone side of the test sample, and permitting air from the air flow toexit the cavity from the other side of the test sample; and measuringthermal properties of the test sample using each of the air flow andtemperatures of the respective first and second plates.

In other example embodiments of this invention, there is provided adynamic heat flow meter for measuring thermal properties of insulation,the dynamic heat flow meter comprising: a housing defining at least onecavity therein; first and second plates at least partially provided inthe housing, wherein a test sample of insulation is to be providedbetween the first and second plates; means for providing the first andsecond plates at known, but different, temperatures when the test sampleis therebetween; means for introducing an air flow into the cavity onone side of the test sample, and permitting air from the air flow toexit the cavity from the other side of the test sample; and means formeasuring thermal properties of the test sample using each of the airflow and temperatures of the respective first and second plates

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a conventional steady state or staticheat flow meter.

FIG. 2 is a schematic diagram of a dynamic heat flow meter according toan example embodiment of this invention.

DETAILED DESCRIPTION OF THE INVENTION

In certain example embodiments of this invention, the aforesaid problemsof static or steady-state heat flow meters are addressed and overcome byproviding a heat flow meter which intentionally introduces a measuredair flow adjacent the test sample (e.g., insulation product such asfiberglass insulation batt, loose-fill fiberglass insulation, loose-fillcellulose insulation, combination or laminate of fiberglass and foaminsulation, etc.) to be measured. The air flow may be through and/oracross the test sample. The heat flow meter then measures thermalproperties (e.g., thermal conductivity and/or heat capacity) of the testsample taking into account air flow through the test sample.

Since an intentionally introduced and measured air flow, which air flowat least partially proceeds through the test sample, is taken intoaccount, one can determine how effective the particular sample would bein real-world conditions where wind (and thus air flow in/through homewalls) is a frequent occurrence. This permits one to determine whichtypes of insulation may be effective in certain types of environments.

FIG. 2 is a schematic diagram illustrating a dynamic heat flow meteraccording to an example embodiment of this invention. The test sample orspecimen (1) to be measured may be an insulation product such asfiberglass insulation batt, loose-fill fiberglass insulation, loose-fillcellulose insulation, combination or laminate of fiberglass and foaminsulation, etc. The test sample (1) to be measured is located betweentwo flat plates (2) and (3), and the plates are maintained at known, butdifferent, temperatures. One plate (2) may be considered a hot plate,and the other (3) a cold plate since one is hotter than the other. Asheat flows through the test sample (1) from the hot side to the coldside, it is possible for a heat flux transducer (not shown) to measurethe amount of heat transferred. Thermocouple(s), thermistor(s), or othertemperature measuring device(s) (5) measure the temperatures of each ofthe two plates (2 and 3).

Still referring to FIG. 2, one or more aperture(s) may be provided inone of the plates (2 or 3) so as to allow a measured air flow from airflow input 7 to be introduced into a cavity of the measuring device andbe directed toward and/or adjacent the test sample to be measured. Theinput air flow is measured (e.g., by volume). For example and withoutlimitation, an example introduced air flow may be about 3 or 4 cubicfeet per minute. The input air flow may be introduced either through anaperture(s) in the cold plate (3) as shown in FIG. 2, or alternativelythrough an aperture(s) in the hot plate (2) (i.e., it may be introducedfrom either side). At least part of, and preferably all of, the air flowthat is introduced from input 7 through the aperture(s) in the plateflows through the test sample 1 and exits the heat flow meter via one ormore aperture(s) in the other plate (e.g., see air flow output in FIG.2).

The housing 10 surrounding the plates and test sample prevents any airflow from leaking out of the device, so that all or substantially all ofthe introduced air flow is forced to flow through the test sample 1. Incertain example instances, a gasket(s) may be provided to improve theseal and make sure than air flow does not escape except through adesigned air flow outlet(s). If the air flow volume measuring device 11at the air flow outlet measures air flow at an amount more than apredetermined amount different than does an air flow volume measuringdevice (not shown) at the inlet proximate 7, then an alarm may beactuated to indicate that an air flow leak is present in this system.

Temperature measuring device(s) (5) measure the temperature of each ofthe hot plate, the cold plate, the input air flow, and the output airflow. This information may be used in equation(s) in determining thethermal properties of the test sample.

FIG. 2 illustrates the measured air flow moving through the test sample,in a direction which is parallel to, or anti-parallel to, the heat-flowdirection. The air is introduced into the cavity of the meter from anexternal temperature controlled source. The heat-flow meter withcontrolled air flow is used to determine total heat-flow rates as afunction of air-flow rate, air flow direction, and temperature forcommonly used wall cavity insulations for example. It is noted, however,that the direction of air flow in other embodiments may be in differentdirections.

The heat flow meter thus measures thermal properties (e.g., thermalconductivity and/or heat capacity) of the test sample taking intoaccount air flow through the test sample. For example, if thermalconductivity can be measured as discussed above, with a known andmeasured air flow through and/or across the test sample 1, the productsthermal properties can be determined as a function of air flow.

In certain example embodiments, the intentionally input measured airflow may be introduced into the cavity of the heat flow meter via anaperture(s) in housing 10, instead of an aperture(s) in one of theplates (2 or 3). Thus, in such embodiments, no aperture(s) in plate (3)is needed. It is also possible for the air flow outlet aperture(s) to bedefined in housing 10 instead of in one of the plates (2 or 3), so longas the air flow inlet and air flow outlet are provided on opposite sidesof the test sample 1. Thus, in certain example embodiments of thisinvention, there need not be any holes or aperture(s) in plate (2)and/or plate (3).

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

1. A dynamic heat flow meter for measuring thermal properties ofinsulation, the dynamic heat flow meter comprising: a housing definingat least one cavity therein; first and second plates at least partiallyprovided in the housing, wherein a test sample of insulation is to beprovided between the first and second plates; means for providing thefirst and second plates at known, but different, temperatures when thetest sample is therebetween; means for introducing an air flow into thecavity on one side of the test sample, and permitting air from the airflow to exit the cavity from the other side of the test sample; meansfor measuring thermal properties of the test sample using each of theair flow and temperatures of the respective first and second plates; andwherein the first plate has an air flow inlet aperture(s) definedtherein, and the second plate has an air flow outlet aperture(s) definedtherein.
 2. The heat flow meter of claim 1, wherein the test sampleincludes at least fiberglass insulation.
 3. A dynamic heat flow meterfor measuring thermal properties of insulation, the dynamic heat flowmeter comprising: a housing defining at least one cavity therein; firstand second plates at least partially provided in the housing, wherein atest sample of insulation is to be provided between the first and secondplates; means for providing the first and second plates at known, butdifferent, temperatures when the test sample is therebetween; means forintroducing an air flow into the cavity on one side of the test sample,and permitting air from the air flow to exit the cavity from the otherside of the test sample; means for measuring thermal properties of thetest sample using each of the air flow and temperatures of therespective first and second plates; and wherein the housing has an airflow inlet aperture(s) defined therein on a first side of the testsample, and the housing further has an air flow outlet aperture(s)defined therein on a second side of the test sample that is opposite thefirst side.
 4. The heat flow meter of claim 3, wherein the test sampleincludes at least fiberglass insulation.
 5. A dynamic heat flow meterfor measuring thermal properties of insulation, the dynamic heat flowmeter comprising: a housing defining at least one cavity therein; firstand second plates at least partially provided in the housing, wherein atest sample of insulation is to be provided between the first and secondplates; means for providing the first and second plates at known, butdifferent, temperatures when the test sample is therebetween; means forintroducing an air flow into the cavity on one side of the test sample,and permitting air from the air flow to exit the cavity from the otherside of the test sample; means for measuring thermal properties of thetest sample using each of the air flow and temperatures of therespective first and second plates; and means for measuring the volumeof air flow both entering and exiting the cavity of the meter.
 6. Theheat flow meter of claim 5, wherein the first plate has an air flowinlet aperture(s) defined therein, and the second plate has an air flowoutlet aperture(s) defined therein.
 7. The heat flow meter of claim 5,wherein the test sample includes at least fiberglass insulation.
 8. Adynamic heat flow meter for measuring thermal properties of insulation,the dynamic heat flow meter comprising: a housing defining at least onecavity therein; first and second plates at least partially provided inthe housing, wherein a test sample of insulation is to be providedbetween the first and second plates; means for maintaining the first andsecond plates at different temperatures when the test sample istherebetween; an inlet for introducing a measured and/or known volume ofair flow into the cavity on one side of the test sample; at least onecircuit for measuring thermal properties of the test sample taking intoaccount each of the air flow and temperatures of the respective firstand second plates; and wherein the housing has an air flow inletaperture(s) defined therein on a first side of the test sample, and thehousing further has an air flow outlet aperture(s) defined therein on asecond side of the test sample that is opposite the first side.
 9. Amethod of measuring thermal properties of insulation, the methodcomprising: in a housing, providing first and second plates; positioninga test sample of insulation between the first and second plates;providing the first and second plates at different temperatures when thetest sample is therebetween; introducing an air flow into the cavity onone side of the test sample, and permitting air from the air flow toexit the cavity from the other side of the test sample; measuringthermal properties of the test sample using each of the air flow andtemperatures of the respective first and second plates; and wherein thefirst plate has an air flow inlet aperture(s) defined therein, and thesecond plate has an air flow outlet aperture(s) defined therein.
 10. Themethod of claim 9, wherein the test sample includes each of fiberglassinsulation and foam insulation.
 11. The method of claim 9, wherein thetest sample includes at least fiberglass insulation.
 12. A method ofmeasuring thermal properties of insulation, the method comprising: in ahousing, providing first and second plates; positioning a test sample ofinsulation between the first and second plates; providing the first andsecond plates at different temperatures when the test sample istherebetween; introducing an air flow into the cavity on one side of thetest sample, and permitting air from the air flow to exit the cavityfrom the other side of the test sample; measuring thermal properties ofthe test sample using each of the air flow and temperatures of therespective first and second plates; and wherein the housing has an airflow inlet aperture(s) defined therein on a first side of the testsample, and the housing further has an air flow outlet aperture(s)defined therein on a second side of the test sample that is opposite thefirst side.
 13. The method of claim 12, wherein the test sample includesat least fiberglass insulation.
 14. A method of measuring thermalproperties of insulation, the method comprising: in a housing, providingfirst and second plates; positioning a test sample of insulation betweenthe first and second plates; providing the first and second plates atdifferent temperatures when the test sample is therebetween; introducingan air flow into the cavity on one side of the test sample, andpermitting air from the air flow to exit the cavity from the other sideof the test sample; measuring thermal properties of the test sampleusing each of the air flow and temperatures of the respective first andsecond plates; and measuring the volume of air flow both entering andexiting the cavity of the meter.
 15. The method of claim 14, wherein thefirst plate has an air flow inlet aperture(s) defined therein, and thesecond plate has an air flow outlet aperture(s) defined therein.
 16. Themethod of claim 14, wherein the test sample includes at least fiberglassinsulation.